<template>
    <div class="container">
        <el-row>
            <!-- 左侧面板 -->
            <el-col :span="6">
                <el-card>
                    <!-- 这里可以放置左侧面板的内容 -->
                    <el-tree :data="data" show-checkbox node-key="id" default-expand-all :expand-on-click-node="false">
                        <span class="custom-tree-node" slot-scope="{ node, data }">
                            <span>{{ node.label }}</span>
                            <span>
                                <el-button type="text" size="mini" @click="() => append(data)">
                                    Append
                                </el-button>
                                <el-button type="text" size="mini" @click="() => remove(node, data)">
                                    Delete
                                </el-button>
                            </span>
                        </span>
                    </el-tree>
                </el-card>
            </el-col>
            <!-- 右侧列表框 -->
            <el-col :span="18">
                <el-card>
                    <!-- 这里可以放置右侧列表框的内容 -->
                    <el-select v-model="selectedItem" placeholder="请选择项目">
                        <el-option label="项目1" value="1"></el-option>
                        <el-option label="项目2" value="2"></el-option>
                        <el-option label="项目3" value="3"></el-option>
                    </el-select>
                </el-card>
            </el-col>
        </el-row>
    </div>
</template> 
<script>
  let id = 1000;

  export default {
    data() {
      const data = [{
        id: 1,
        label: '一级 1',
        children: [{
          id: 4,
          label: '二级 1-1',
          children: [{
            id: 9,
            label: '三级 1-1-1'
          }, {
            id: 10,
            label: '三级 1-1-2'
          }]
        }]
      }, {
        id: 2,
        label: '一级 2',
        children: [{
          id: 5,
          label: '二级 2-1'
        }, {
          id: 6,
          label: '二级 2-2'
        }]
      }, {
        id: 3,
        label: '一级 3',
        children: [{
          id: 7,
          label: '二级 3-1'
        }, {
          id: 8,
          label: '二级 3-2'
        }]
      }];
      return {
        data: JSON.parse(JSON.stringify(data))
      }
    },

    methods: {
      append(data) {
        const newChild = { id: id++, label: 'testtest', children: [] };
        if (!data.children) {
          this.$set(data, 'children', []);
        }
        data.children.push(newChild);
      },

      remove(node, data) {
        const parent = node.parent;
        const children = parent.data.children || parent.data;
        const index = children.findIndex(d => d.id === data.id);
        children.splice(index, 1);
      },

      renderContent(h, { node, data, store }) {
        return (
          <span class="custom-tree-node">
            <span>{node.label}</span>
            <span>
              <el-button size="mini" type="text" on-click={ () => this.append(data) }>Append</el-button>
              <el-button size="mini" type="text" on-click={ () => this.remove(node, data) }>Delete</el-button>
            </span>
          </span>);
      }
    }
  };
</script>